Multiphysics multilayer modelling and simulation of HTS REBCO magnets carrying direct currents under AC magnetic fields

High temperature superconducting homopolar inductor machine (HTS-HIM) is concerned and studied for electric aircraft because of its high power density, high efficiency, and high power-to-weight ratio. In an HTS-HIM, the high temperature superconducting magnets carrying DC currents under alternating background magnetic fields work as excitation magnets. Under extreme electromagnetic conditions, the voltage, loss, and temperature of the HTS magnets will increase because of the dynamic resistance effect. To predict the behaviors of the HTS magnet, it is necessary to analyze its electromagnetic-thermal characteristics by using a multiphysics model. This paper establishes a 2D axisymmetric multilayer multiphysics HTS magnet model based on the H-formulation. By using this multilayer multiphysics model, the electromagnetic-thermal characteristics of each turn can be analyzed. Meanwhile, this model can not only analyze the total loss and loss components of each layer under various operating conditions but also predict the temperature and quench behaviors of each part. The result shows that the loss components of the REBCO layer have distinct temperature dependence. When considering the thermal field effect, the magnetization loss of the REBCO layer reduces by 75% and the transport loss of the REBCO layer increases by 45% under high direct currents and high AC magnetic fields. Meanwhile, the temperature of the external turn is higher than the internal turn, and the external turn is at risk of quench in the operating process when the direct currents and AC magnetic fields are high. The multilayer multiphysics model is a powerful tool for designing, analyzing, and optimizing the HTS magnets in HTS-HIMs, and this multiphysics modelling technique can be utilized in modelling and simulating HTS REBCO magnets in various applications.